JPH0659191A - Zoom lens - Google Patents

Abstract

(57) [Summary] [Purpose] A variable power ratio of 18 is obtained by appropriately setting the lens configuration and aspherical surface of each lens group having four lens groups.
To obtain a zoom lens suitable for a television camera having a large aperture of about 40 and an F number of about 1.6 and a high zoom ratio. [Structure] The first positive lens that is fixed when zooming in order from the object side.
It has a group, a negative second group for zooming, a positive third group that corrects image plane variation due to zooming, and a fixed positive fourth group, and the second and third groups are variable magnifications. At that time, the imaging magnification changes within a region including the same magnification, and at least one lens surface is defined by the maximum incident height at the time of varying the axial ray to the third group and the maximum incident height at the telephoto end. The aspherical surface is applied to the focal lengths fW and fT of the entire system at the wide-angle end and the telephoto end, the zoom ratio Z, the F-numbers FNW and FNT at the wide-angle end and the telephoto end, the focal lengths of the first group and the F-numbers f1 and FN1, Refractive index difference Δn3 of the medium before and after the cemented lens surface in the third group, focal length f3 and F number FN
Properly set 3 etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and in particular, by appropriately using an aspherical surface as part of the lens system, the F number at the wide-angle end has a large aperture of 1.6 and a zoom ratio of 18. The present invention relates to a zoom lens suitable for a television camera, a photographic camera, a video camera, or the like, which has good optical performance over a wide zoom range of about 5 to 44.

[0002]

2. Description of the Related Art Conventionally, a television camera or a camera for photography,
A zoom lens having a large aperture, a high zoom ratio and high optical performance is required for a video camera or the like.

Of these, particularly in a color television camera for broadcasting, operability and mobility are emphasized, and in response to the demand, the image pickup device has recently been a small CCD (solid-state image pickup device) of 2/3 inch or 1/2 inch. Is becoming mainstream.

Since this CCD has a substantially uniform resolving power over the entire imaging range, it is required for a zoom lens using this CCD that the resolving power is substantially uniform from the center of the screen to the periphery of the screen.

For example, various aberrations such as astigmatism, distortion, and chromatic aberration of magnification are satisfactorily corrected, and it is desired that the entire screen has high optical performance. Further, it is required to have a high zoom ratio, be small and lightweight, and have a long back focus because a color separation system and various filters are arranged in front of the image pickup means.

In the zoom lens, from the object side, in order from the object side, a first group of positive refracting power for focusing (focusing), a second group of negative refracting power for zooming, and an image plane that varies with zooming. A so-called four-group zoom lens composed of four lens groups of a third lens group having a positive or negative refractive power for correcting the above and a fourth lens group having a positive refractive power for image formation has a relatively high zoom ratio and a large zoom lens. Since it is easy to adjust the aperture ratio, it is widely used in color television cameras for broadcasting.

Of the four-group zoom lens, an F number of 1.6
A large-aperture, high-magnification, four-group zoom lens having a zoom ratio of about 1.8 to about 20 and a zoom ratio of about 20 has been proposed in, for example, JP-A-51-14034.

[0008]

The zoom lens has a large aperture ratio (F number 1.6 to 1.8), a high zoom ratio (zoom ratio 18 to 40), and high optical performance over the entire zoom range. In order to obtain, it is necessary to properly set the refractive power and lens configuration of each lens group.

Generally, in order to obtain high optical performance with little aberration variation over the entire zooming range, it is necessary to increase the degree of freedom in aberration correction by increasing the number of lenses in each lens group, for example.

For this reason, if a zoom lens having a large aperture ratio and a high zoom ratio is to be achieved, the number of lenses will inevitably increase and the size of the entire lens system will increase.

Regarding the image forming performance, there is a problem that the image contrast at the center of the screen is the best, that is, the variation due to the so-called zooming of the best image plane. This is mainly due to the fluctuation of spherical aberration associated with zooming.

In general, when the zoom ratio is Z and the focal length at the wide-angle end is fW, the variation of the spherical aberration due to zooming is fW '= from the wide-angle end where the spherical aberration is 0 as shown in FIG.
Up to around FW × Z ^1/4 , there is an under (minus) tendency with respect to the Gaussian image plane. And the zoom position fW '= f
^Exceeding around W × Z ^1/4 , the amount of under
It becomes 0 at a certain zoom position, and this time it is over (plus)
It becomes a tendency.

Then, the F number becomes larger (the lens system becomes darker), and it becomes the most over (plus) in the vicinity of the zoom position (FNW / FNT) × fT at which F-drop starts, and when the zoom position is passed, the telephoto lens becomes a telephoto lens. The amount of over becomes small toward the end, and becomes almost 0 at the telephoto end.

Generally, the degree of coincidence between the variation due to zooming of the spherical aberration that influences the best image plane at the center of the screen and the variation due to zooming of the sagittal image plane and the meridional image plane that influences the best image plane around the screen is determined. A well-balanced control over the entire zoom range is important for obtaining high optical performance.

In particular, since it is difficult to control the spherical aberration at the zoom position where the F-drop starts, in order to reduce the fluctuation of the spherical aberration, the number of focusing lens groups and the number of lenses of the variable power system are increased and corrected. It was Therefore, there is a problem that the entire lens system becomes large and complicated.

According to the present invention, in the so-called four-group zoom lens, the change of the imaging magnification due to the magnification change of the variable power lens group and the image plane correction lens group, the refractive power of each lens group, the F number value, etc. are appropriately set. At the same time, the incident height when an off-axis light beam or an on-axis light beam passes through the lens surface satisfies at least 1
By applying an aspherical surface to the two lens surfaces, fluctuations in spherical aberration due to zooming are reduced, and in addition, fluctuations in off-axis aberrations such as astigmatism, field curvature, and distortion aberrations due to zooming are well balanced. However, an object of the present invention is to provide a zoom lens having a high zoom ratio with a wide-angle end F number of about 1.6 and a zoom ratio of about 18 to 40, which has high optical performance over the entire zoom range.

[0017]

The zoom lens according to the present invention comprises: (1-a) The first lens unit having a positive refractive power which is fixed during zooming in order from the object side, and the first lens unit having a negative refractive power for zooming. It has two lens units, a third lens unit with a positive refractive power that corrects the image plane variation due to zooming, and a fourth lens unit with a fixed positive refractive power, and the focal lengths of the entire system at the wide-angle end and the telephoto end are respectively fW, fT, the zoom ratio is Z, the F-numbers at the wide-angle end and the telephoto end are FNW and FNT, the focal length and the F-number of the first lens group are f1, FN1, and the second lens group is combined during zooming. The image magnification changes in the area including the same magnification, the lateral magnification change is Z2, and the third group changes the imaging magnification in the area including the same magnification during the magnification change, The maximum incident height upon zooming to the third group and the maximum incident height at the telephoto end are h3m and h3T, respectively. The third group has at least one cemented lens surface, and The refractive index difference between the media before and after the compound lens surface is Δn3, and the focal length and F number of the third lens group are f3 and f3, respectively.
When FN3 is set, 1.25 <FN1 <1.6, where FN1 = f1 / (fT / FNT) ... (1) 5 <Z2 ... (2) 0.2 <Z2 / Z <0.3 (3) 0.8 <FN3 <1.2, where FN3 = f3 ( 2 × h3m) · (4) 0.17 <Δn3 ········· (5), and 1.15 <h3m / h3T in the third group. (6) At least one lens surface satisfying the condition (6) has an aspherical surface.

In particular, the aspherical surface has a shape in which the positive refractive power becomes stronger toward the peripheral portion of the lens, and the aspherical surface amount at 10%, 90%, and 70% of the lens effective diameter of the aspherical surface is ΔX ₁₀ , respectively. Assuming ΔX ₉ and ΔX ₇ 0 <ΔX ₇ / f3 <4 × 10 ⁻⁵ 9 × 10 ⁻⁶ <ΔX ₉ / f3 <3 × 10 ⁻⁴ 3 × 10 ⁻⁵ <ΔX ₁₀ / f3 <6 × 10 It is characterized by satisfying the condition of ^-4 .

(1-b) Focus system in order from the object side,
In a zoom lens composed of a variable power system and a relay system, the focal lengths at the wide-angle end and the telephoto end are fW and fT respectively, the zoom ratio is Z, and the incident height when the maximum field angle light beam at the wide-angle end is incident on the lens surface. hW, focal length fM is fM = fW × Z
When the incident height when the maximum angle of view ray at the ^1/4 zoom position is incident on the lens surface is hM, and the incident height when the maximum axial ray at the telephoto end is incident on the lens surface is hT. 2 <hW / hM, and hT <hW ... (7) At least one lens surface satisfying the condition is aspherical.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are numerical embodiments 1 of the present invention.
It is a lens sectional view in the wide-angle end of 2 and 3.

In FIG. 1 and FIG. 2, F is a focus group (front lens group) having a positive refractive power as the first group, and includes a front group focus group F1 having a negative refractive power and a rear lens group having a positive refractive power. It consists of the group focus group F2. Focusing with a change in the object distance is performed by moving the front focus group F1 on the optical axis.

In the third embodiment of FIG. 3, the focus group F is composed of one lens group, and the entire focus group F is moved on the optical axis for focusing.

V is a variator of negative refracting power for zooming as the second lens unit, which is monotonically moved to the image plane side on the optical axis to move from the wide-angle end (wide) to the telephoto end (tele). I am changing the magnification. C is a compensator having a positive refractive power, which moves non-linearly toward the object side on the optical axis in order to correct the image plane variation due to zooming. The variator V and the compensator C form a variable power system H. The variator V and the compensator C are used in a region where the image forming magnification includes -1 (equal magnification) when changing the magnification. SP (r31) is a diaphragm, and R is a relay group having a positive refractive power. G is a color separation prism, an optical filter or the like, which is shown as a glass block in FIG.

Next, the features of the zoom lens of the present invention will be described.

The present invention has a zoom ratio Z of 10 times or more,
Further, in order to realize a zoom lens having a large aperture in the entire zoom range, first, a bright lens that satisfies the conditional expression (1) is used as the front lens group F. In particular, the F number value FNT at the tele end is made bright. Then, the variator V and the compensator C are each made to pass a point where the image forming magnification is -1 (equal magnification) during zooming, and adopt a zoom system in which each lens group has a high variable magnification.

In particular, the variator V is conditional expression (2),
The variable magnification that satisfies (3) is taken. As a result, the magnification is increased, and the effective F number value FN3 of the compensator is maintained bright so as to satisfy the conditional expression (4), and the enlargement of the diameter is facilitated. As shown in FIG. 20, among various aberrations that fluctuate due to zooming, spherical aberration that fluctuates greatly near the F drop start point fM is well suppressed.

The height of incidence of the axial ray on the lens group is shown in FIG.
~ As shown in Fig. 23, F at which spherical aberration is most over
It becomes highest at the drop start point (zoom position fM), and becomes lower at other zoom regions. 21 to 23 show an optical path at each zoom position of the optical system of a part of FIG.

In the present invention, by utilizing this optical property, (2-a) the compensator C satisfying the above conditions is provided with a lens surface for correcting spherical aberration. For this reason, at least one cemented lens surface is provided inside the compensator to provide a divergent surface for spherical aberration. At this time, in order to increase the effect of divergence of spherical aberration on the cemented lens surface,
The refractive index difference Δn between the media before and after the boundary surface is set to 0.17 <Δn (5) as in conditional expression (5). As a result, the fluctuation of spherical aberration due to zooming in the low-order region is well corrected.

Since the effective F number FN3 of the compensator C for the zoom lens according to the present invention is extremely bright, high-order spherical aberration is overcorrected. Therefore, the design of only spherical lenses is the limit for increasing the aperture.

Therefore, in the present invention, in the (2-b) compensator C, the maximum incident height h3m of the axial ray appearing at the F drop start point and the F end at the telephoto end.
The ratio of the axial ray incident height h3T which becomes lower due to the drop is 1.15 <h3m / h3T (6) as shown in conditional expression (6). I am giving it. This cancels the remaining high-order spherical aberration.

In order to satisfactorily correct particularly high-order spherical aberration, the central portion of the aspherical surface is substantially spherical, and the aspherical surface becomes larger toward the periphery.

It should be noted that the above conditional expression exerts the effect of an aspherical surface only in a small part of the zoom range near the F drop start point in the zoom system of the zoom lens, and in the other zoom regions, it becomes a spherical surface. This is for minimizing the influence on aberration and astigmatism.

The fact that the ratio of h3m and h3T is close to 1 in the conditional expression (6) means that the change of the incident height of the axial ray on the aspherical surface is small from the vicinity of the F drop start point to the tele end. The effect of spherical aberration correction by the spherical surface is F
Not only the vicinity of the drop start point but also the spherical aberration at the telephoto end will be affected.

This is because of the aspherical surface, the zoom position fM (=
When the spherical aberration at (FNW / FNT) × fT) is corrected in the under direction, the spherical aberration at the tele end also changes in the under direction due to the influence of this aspherical surface, and the effect of correcting the spherical aberration variation is obtained. It's not good because it means getting weaker.

As described above, in the present embodiment, the aspherical lens surface is appropriately set to reduce the influence of spherical aberration at the telephoto end, correct spherical aberration near the F drop, and spherical surface over the entire zoom range. Corrects aberrations well.

Next, features of each embodiment of the present invention will be described.

The first embodiment shown in FIG. 1 has a zoom ratio of more than 18 times, and R1 to R7 are the front focus group F1 for focusing and have a negative power (refractive power) as a whole. R8 to R16 are for focus and zoom,
This is a fixed rear focus group F2, and has positive power as a whole. R1 to R16 function as the front lens group F having a function of connecting an object point to the variator V,
The entire front lens group F has a loose positive power.

R17 to R23 mainly contribute to zooming, and when zooming from wide to tele, it moves monotonically to the image side,
It is a variator that passes an imaging magnification of -1x (equal magnification) on the way. R24 to R30 are compensators mainly having a variable power and an image point correction function associated with the variable power, and have a positive power. When zooming from wide to tele, they move monotonically to the object side and are connected in the middle. Image magnification-1x is passed. SP (R3
1) is a diaphragm. R32 to R45 are a relay group having an image forming action, and R46 to R47 are glass blocks equivalent to a color separation prism.

In the first embodiment, in order to increase the magnification, the variator V has a magnifying effect of 5.31 times and the compensator C also contributes to the magnifying power of 3.45 at all magnifications. .

When the F number FN1 of the front lens group is defined as FN1 = f1 (fT / FNT) as an index for increasing the aperture, FN1 = 1.62 in this embodiment.
When maintaining the F number of this front lens group in the entire zoom range, the F number FN3 of the compensator C is changed to FN3.
= F3 / (2 × h3m), FN3 = 1.07
That is a large aperture ratio.

In contrast to these large aperture ratios, in the front lens group, the front lens group is used to correct the spherical aberration on the tele side, and the front lens group F1 has a negative power and the rear lens group F2 has a positive power. It is divided into two groups. Then, each lens group is composed of multiple elements to share and correct spherical aberration, and a cemented lens surface is applied to each lens group and spherical aberration in the front lens group is applied by a method such as divergence of spherical aberration. The occurrence of is suppressed.

Generally, it is preferable that the compensator C and the variator V have a simple lens structure and a small block thickness in order to downsize the entire zoom lens system and save power in the drive system. Therefore, in the compensator C, it is desired to reduce the number of lenses as much as possible.

On the other hand, as mentioned above, the F number FN3 of the compensator C is very bright,
It becomes difficult to correct high-order aberrations in the compensator group C, and the spherical aberration greatly changes especially at the zoom position near the F-drop.

Therefore, in this embodiment, the first lens of the compensator is a positive lens having a convex surface facing the image surface side, then a lens having a concave cemented lens surface on the object side, and then on the object side. By constructing a positive lens with the convex surface facing, the occurrence of spherical aberration is suppressed. Further, assuming that the refractive index difference between the front and rear media is Δn on the cemented lens surface, Δn = 1.70 is set to increase the effect as a surface for diverging spherical aberration.

The aspherical surface is applied to the R29 surface, and the above conditional expression (6) is h3m / h3T = 1.25. The direction of the aspherical surface is the direction in which the positive power becomes stronger as the on-axis incident height becomes higher, in order to avoid abrupt changes in the aspherical shape and to efficiently correct spherical aberration from low-order to high-order regions. In addition, spherical aberration is mainly corrected by using only the aspherical coefficients C and D. The amount of aspherical surface at this time is 6.2 μm, which is 100% of the effective diameter.

The second embodiment shown in FIG. 2 has a zoom ratio of 17 times. Compared with the first embodiment, the F-drop of the amount of decrease in the F-number is reduced to reduce the portion where the axial ray passes only in the vicinity of the F-drop start point in the compensator. That is,
Despite reducing the value of h3m / h3T and reducing the degree of freedom in designing the front lens group, a small amount of aspherical surface suppresses variation in spherical aberration over the entire zoom range.

R1 to R6 are the front focus group F1 for focusing, which has a negative power and R7 to R6.
Reference numeral 15 denotes a rear group focus group that is fixed during focusing and zooming, and has a positive power. R1 to R15 function as the front lens group and have a loose positive power.

R16 to R22 mainly contribute to zooming, and when zooming from wide to tele, they move monotonically to the image side,
It is a variator that passes an imaging magnification of -1x (equal magnification) on the way. R23 to R29 are compensators mainly having the effects of zooming and image point correction, have positive power, and monotonously move to the object side when zooming from the wide end to the tele end,
On the way, the image formation magnification of -1x is passed. SP (R30) is a diaphragm, R31 to R44 are relay groups having an image forming action, and R45 to R46 are glass blocks equivalent to color separation prisms.

In this embodiment, in order to increase the magnification, the variator V has a variable magnification effect of 4.99 times, and at the same time, the compensator also contributes to a variable magnification of 3.41 times.

The F number FN1 of the front lens group F is FN1 = 1.55, and the F number F of the compensator C is F.
N3 is FN3 = 0.99, which is a larger aperture ratio.

In the compensator C in this embodiment, as in the first embodiment, the first lens is a positive lens with the convex surface facing the image side, and then the cemented lens surface having a concave surface is arranged on the object side. Next, a positive lens having a convex surface facing the object side is used to suppress the occurrence of spherical aberration. Further, the difference in refractive index between the media before and after the bonding surface is Δn = 1.70, which allows spherical aberration to be corrected well.

At this time, the aspherical surface in the compensator C is given to the R25 surface, and h3m / h3T = 1.1.
It becomes 9. The direction of the aspherical surface is such that the positive power becomes stronger as the on-axis incident height becomes higher. However, since a larger effect is obtained with a small amount of the aspherical surface, the refractive index of the aspherical surface is larger than that of the first embodiment. Is higher.

Since the ratio of h3m / h3T is small, the spherical aberration in the vicinity of the F drop start point is controlled by increasing the aspherical surface design freedom and improving the aspherical surface efficiency. Of the aspherical coefficients in the spherical formula,
Good results have been obtained by using C, D, and E up to a high order range of h ¹⁰ . The aspheric amount at this time is 10 of R25.
The height is about 2 μm.

In the third embodiment shown in FIG. 3, the zoom lens has a very high zoom ratio of 44 times,
The F number FNT at the tele end is 3.0, which is very bright. R1 to R8 are front lens groups (focus group F), which move during focusing and are fixed during zooming. In order to reduce the secondary spectrum, a plurality of convex lenses having an Abbe number νd exceeding 80 are arranged in the front lens group F, and a lens having an Abbe number νd exceeding 95 is used therein. The front lens group F has a loose positive power as a whole.

R9 to R15 are mainly variators that contribute to zooming and move monotonically to the image plane side during zooming from wide to tele, and pass through the imaging magnification -1 × (equal magnification) on the way. is there. R16 to R25 are compensators that mainly have a function of zooming and image point correction, have positive power, and move monotonically toward the object side during zooming from the wide end to the tele end, and the image forming magnification in the middle. Pass -1x. SP (R26) is a diaphragm. R27 to R42 are a relay group having an image forming action, and R43 to R44 are glass blocks equivalent to a color separation prism.

In this embodiment, in order to increase the magnification, the variator has a zooming effect of 9.20 times, and at the same time, the compensator also contributes to a zooming of 4.78 times.

Further, F of the front lens group F in this embodiment is
The number FN1 is FN1 = 1.28, and the compensator F number FN3 is FN3 = 0.83, which is very bright.

As a solution for reducing the variation of spherical aberration in the present embodiment, the point is to search for a solution of a compensator having a brightness of FN3 = 0.83.

First, the first lens of the compensator group is a positive lens having a convex surface facing the image surface side, and then a first cemented lens surface having a concave surface facing the image surface side. Next, a second cemented lens surface having a concave surface facing the object side is arranged, and then a positive lens having a convex surface facing the object side is formed, that is, a symmetrical shape is formed in the compensator group. Generation of spherical aberration is suppressed by increasing the degree of freedom.

At this time, the second cemented lens surface has a difference Δn in refractive index between the front and rear media up to Δn = 0.23 to increase the effect of the spherical aberration diverging surface. At this time, the achromatization inside the compensator group is achieved by separating the Abbe number νd of the lens cemented at the second cemented lens surface, but only the second cemented lens surface can make the cemented lens surface Since the radius of curvature of the compensator becomes tight and the spherical aberration is adversely affected, the achromatism in the compensator group is also burdened to the first cemented lens to suppress the occurrence of aberration in the compensator group in a well-balanced manner.

The aspherical surface in this embodiment is applied to the lens surface of R24. Since the value of h3m / h3T in this example is h3m / h3T = 1.5, the range in which the axial ray passes only near the F drop start point is wider than in the other examples, and the effect of the aspherical surface is obtained. It will be easier. Therefore, R2
Since the aspherical surfaces on the four surfaces can be corrected for aberrations with a very simple shape, various aberrations can be corrected with a very small degree of freedom of the aspherical surface, in which only D is used among the aspherical surface coefficients in the above aspherical surface formula. Have control. The aspherical amount at this time is about 27 μm, which is 100% of the effective diameter of R24.

FIG. 24 is a lens sectional view at the wide-angle end according to Numerical Embodiment 4 of the present invention.

In FIG. 24, F is a focus group (front lens group) having a positive refractive power as the first group, and the front group focus group F1 having a negative refractive power and the rear group focus group F2 having a positive refractive power. And consists of. Focusing with a change in the object distance is performed by moving the front focus group F1 on the optical axis.

V is a variator of negative refracting power for zooming as the second lens unit, which is monotonically moved to the image plane side on the optical axis to change from the wide-angle end (wide) to the telephoto end (tele). Have doubled. C is a compensator having a positive refractive power, which moves non-linearly toward the object side on the optical axis in order to correct the image plane variation due to zooming. The variator V and the compensator C form a variable power system H. The variator V and the compensator C are used in a region where the image forming magnification includes -1 (equal magnification) when changing the magnification. SP (r31) is a diaphragm, and R is a relay group having a positive refractive power. G is a color separation prism, an optical filter or the like, which is shown as a glass block in FIG.

In this embodiment, in the so-called four-group zoom lens having the above-described structure, at least one lens surface of the entire zoom lens system which satisfies the above-mentioned conditional expression (7) is provided with an aspherical surface of a predetermined shape. There is. As a result, various aberrations such as astigmatism, field curvature, and spherical aberration when achieving a large aperture ratio and a high zoom ratio are satisfactorily corrected, and high optical performance is obtained over the entire zoom range.

In Numerical Embodiment 4 of the present invention, an aspherical surface is applied to the seventeenth lens surface R17 in consideration of the ratio of the incident heights hW and hM which satisfy the above-mentioned conditional expression (7). As a result, the astigmatism at the wide-angle end (focal length 12.2) becomes under, and the fluctuation of the astigmatism between the focal lengths fW and fM is reduced. Corrected in good balance.

Generally, in the zoom lens, the image forming performance around the screen is largely affected by the fluctuations of astigmatism and distortion associated with zooming.

FIGS. 30A and 30B are explanatory views showing fluctuations of astigmatism and distortion associated with typical zooming in a so-called four-group zoom lens, with the horizontal axis representing the zoom position. is there.

Now, let us say that the zoom ratio is Z and the focal length at the wide-angle end is fW. At this time, the astigmatism (meridional image plane) has a focal length f from the wide-angle end as shown in FIG.
The correction is insufficient (under) for the Gaussian image plane up to the zoom position of M = fW × Z ^1/4 .

The under amount decreases as going from the zoom position of the focal length fM to the telephoto side, and becomes overcorrected at a certain zoom position. Then, the F-number of the entire system changes, and it becomes the most over near the zoom position (focal length fMM) where the lens system becomes dark, and then decreases toward the telephoto side, and at the telephoto end (focal length fT).
Becomes almost zero.

The variation of astigmatism (image plane characteristic) that influences the image forming performance in the periphery of the screen due to such variation of magnification and the variation of spherical aberration that influences the best image plane at the center of the screen over the entire variation range. Matching is important for maintaining good optical performance. If the astigmatism and the spherical aberration do not match at this time, good optical performance cannot be obtained over the entire screen.

Generally, it is difficult to match astigmatism and spherical aberration over the entire zoom range.

On the other hand, as shown in FIG. 30 (B), the distortion is considerably large negative at the wide-angle end (focal length fW). Then, as it goes from the wide-angle end (fW) to the telephoto side (fT), it gradually increases in the positive direction, passes through the zoom position where the distortion aberration is 0, and the positive value becomes maximum at the focal length fM. Then, the focal length fM gradually decreases from the telephoto end (fT).

Therefore, according to the present invention, by applying an aspherical surface of a predetermined shape to at least one lens surface satisfying the conditional expression (7), the astigmatism between the zoom positions of the focal length fW and the focal length fM at the wide-angle end is obtained. Changes in aberration and distortion are reduced.

The solid line in FIG. 31A shows how the astigmatism (meridional image plane) is first corrected at the wide-angle end by using the aspherical surface at this time.

Conditional expression (7) introduces an aspherical surface into the lens surface where the effective diameter of a single lens is determined in a part of the entire variable power range in the variable power system and the zoom system of the zoom lens. , The lens surface that can suppress the aberration variation due to the focusing system and the zooming system as much as possible is specified. After correcting the astigmatism at the wide-angle end on the aspherical surface, the relay system restores the desired balance of the aberration at the wide-angle end to the desired balance, and as shown by the solid line in FIG. The variation of astigmatism is well corrected.

On the other hand, in the 4-group zoom lens, when the focal length shifts from the wide-angle side to the telephoto side, the incident height of axial rays gradually increases. At this time, the spherical aberration on the telephoto side does not always match the direction of the spherical aberration on the telephoto side when the aspherical surface is introduced to correct the astigmatism at the wide-angle end.

Therefore, in the present invention, the lens surface provided with the aspherical surface is limited by the condition of hW / hT.

However, when the astigmatism due to the aspherical surface and the direction of improvement of the spherical aberration coincide with each other, on-axis rays and off-axis rays close to the optical axis are introduced by introducing a low-order aspherical term due to the property of the aspherical surface. Can be controlled.

At this time, spherical aberration on the telephoto side is corrected at a portion of the lens surface having an aspherical surface where the on-axis incident height and the off-axis incident height are lower than the incident height hT, and from the incident height hT, it is corrected. Astigmatism on the wide-angle side is corrected in the high portion.

As described above, in this embodiment, the aberration fluctuations in the focusing system and the zooming system including the relay system are satisfactorily corrected, thereby obtaining good optical performance in the entire zooming range.

Next, numerical examples of the present invention will be shown. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air gap from the object side, and Ni and νi are respectively from the object side of the i-th lens. The refractive index of glass and the Abbe number.

The aspherical shape has an X axis in the optical axis direction, an H axis in the direction perpendicular to the optical axis, a positive light traveling direction, and R as a paraxial radius of curvature.
When A, B, C, D, and E are aspherical coefficients, respectively

[0084]

[Equation 1] It is expressed by Numerical Example 1 F = 12.2 to 223.46 FNO = 1: 1.6 to 2.2 2 ω = 66.5 ° to 4.2 ° R 1 = 2455.41 D 1 = 5.40 N 1 = 1.69979 ν 1 = 55.5 R 2 = 271.91 D 2 = 28.94 R 3 = -267.58 D 3 = 3.00 N 2 = 1.69979 ν 2 = 55.5 R 4 = -2503.19 D 4 = 1.98 R 5 = 9738.25 D 5 = 3.00 N 3 = 1.64254 ν 3 = 60.1 R 6 = 224.83 D 6 = 14.59 N 4 = 1.76168 ν 4 = 27.5 R 7 = 1879.70 D 7 = 1.84 R 8 = 1282.45 D 8 = 13.52 N 5 = 1.62286 ν 5 = 60.3 R 9 = -242.57 D 9 = 0.30 R10 = 1074.61 D 10 = 4.50 N 6 = 1.81265 ν 6 = 25.4 R11 = 150.07 D 11 = 20.80 N 7 = 1.48915 ν 7 = 70.2 R12 = -401.90 D 12 = 0.30 R13 = 160.26 D 13 = 16.10 N 8 = 1.48915 ν 8 = 70.2 R14 = 45982.91 D 14 = 0.30 R15 = 148.13 D 15 = 12.92 N 9 = 1.62286 ν 9 = 60.3 R16 = 512.54 D 16 = Variable R17 = 95.44 D 17 = 2.40 N10 = 1.77621 ν10 = 49.6 R18 = 42.25 D 18 = 9.16 R19 = -1689.53 D 19 = 2.20 N11 = 1.77621 ν11 = 49.6 R20 = 84.69 D 20 = 11.71 R21 = -46.36 D 21 = 2.20 N12 = 1.77621 ν12 = 49.6 R22 = 779.13 D 22 = 5.58 N13 = 1.93306 ν13 = 21.3 R23 = -92.60 D 23 = variable R24 = 1110.01 D 24 = 8.90 N14 = 1.48915 ν14 = 70.2 R25 = -82.8 6 D 25 = 0.30 R26 = 325.37 D 26 = 12.18 N15 = 1.64254 ν15 = 60.1 R27 = -71.86 D 27 = 2.40 N16 = 1.81265 ν16 = 25.4 R28 = -222.32 D 28 = 0.30 R29 = (84.97) D 29 = 9.95 N17 = 1.48915 ν17 = 70.2 Aspheric surface R30 = -1089.44 D 30 = Variable R31 = (Aperture) D 31 = 5.46 R32 = -50.46 D 32 = 1.40 N18 = 1.65425 ν18 = 58.5 R33 = 40.07 D 33 = 5.03 N19 = 1.70443 ν19 = 30.1 R34 = 68.80 D 34 = 9.57 R35 = -39.21 D 35 = 1.50 N20 = 1.64254 ν20 = 60.1 R36 = -900.35 D 36 = 9.72 N21 = 1.69417 ν21 = 31.1 R37 = -37.65 D 37 = 34.00 R38 = 70.67 D 38 = 12.47 N22 = 1.48915 ν22 = 70.2 R39 = -90.22 D 39 = 0.20 R40 = -501.75 D 40 = 2.00 N23 = 1.81265 ν23 = 25.4 R41 = 57.28 D 41 = 2.70 R42 = 110.58 D 42 = 8.02 N24 = 1.48915 ν24 = 70.2 R43 = -75.94 D 43 = 1.10 R44 = 54.30 D 44 = 9.15 N25 = 1.48915 ν25 = 70.2 R45 = 1174.57 D 45 = 8.30 R46 = ∞ D 46 = 69.20 N26 = 1.51825 ν26 = 64.1 R47 = ∞

[0085]

[Table 1] Aspherical shape Reference spherical surface R = 84.973 Parameter ZV = 5.31 Aspherical surface coefficient FN1 = 1.62 A = B = E = 0 FN3 = 1.07 C = 8.0 × 10 ⁻¹² h3m / h3T D = −7.88 × 10 ⁻¹⁶ = 1.25 Δn = 0.170 Aspheric amount h ΔX 70% (21.56) 0.77 μm 90% (27.72) 3.35 μm 100% (30.80) 6 19 μm Numerical Example 2 f = 12.5 to 212.5 fno = 1: 1.6 to 2.0 2 ω = 65.2 ° to 2.2 ° r 1 = 671.00 d 1 = 5.40 n 1 = 1.69979 ν 1 = 55.5 r 2 = 231.23 d 2 = 29.79 r 3 = -209.21 d 3 = 5.009 n 2 = 1.64254 ν 2 = 60.1 r 4 = 217.15 d 4 = 0.26 r 5 = 215.45 d 5 = 14.51 n 3 = 1.76168 ν 3 = 27.5 r 6 = 1673.80 d 6 = 1.84 r 7 = 722.69 d 7 = 14.642 n 4 = 1.62287 n ν 4 = 60.3 r 8 = -239.18 d 8 = 0.30 r 9 = 2027.35 d 9 = 4.50 n 5 = 1.81265 ν 5 = 25.4 r10 = 152.60 d 10 = 20.85 n 6 = 1.48915 ν 6 = 70.2 r11 = -370.46 d 11 = 0.30 r12 = 205.51 d 12 = 14.77 n 7 = 1.48915 ν 7 = 70.2 r 13 = -1091.03 d 13 = 0.30 r14 = 140.50 d 14 = 14.37 n 8 = 1.62287 ν 8 = 60.3 r15 = 648.10 d 15 = variable r16 = 88.91 d 16 = 2.40 n 9 = 1.77621 ν 9 = 49.6 r17 = 41.36 d 17 = 8.20 r18 = -1709.46 d 18 = 2.20 n10 = 1.77621 ν10 = 49.6 r19 = 82.40 d 19 = 12.42 r20 = -48.13 d 20 = 2.20 n11 = 1.77621 ν11 = 49.6 r21 = 447.27 d 21 = 6.43 n12 = 1.93306 ν12 = 21.3 r22 = -100.96 d 22 = Variable r23 = -3606.86 d 23 = 8.89 n13 = 1.48915 ν13 = 70.2 r24 = -82.70 d 24 = 0.30 r25 = 254.65 d 25 = 12.52 n14 = 1.64254 ν14 = 60.1 (aspherical surface) r26 =- 74.51 d 26 = 2.40 n15 = 1.81265 ν15 = 25.4 r27 = -246.12 d 27 = 0.30 r28 = 84.85 d 28 = 10.17 n16 = 1.48915 ν16 = 70.2 r29 = -664.23 d 29 = variable r30 = (aperture) d 30 = 5.46 r31 = -51.38 d 31 = 1.40 n17 = 1.65425 ν17 = 58.5 r32 = 37.53 d 32 = 4.98 n18 = 1.70443 ν18 = 30.1 r33 = 69.05 d 33 = 9.57 r34 = -42.16 d 34 = 1.50 n19 = 1.64254 ν19 = 60.1 r35 =- 1192.59 d 35 = 8.28 n20 = 1.69417 ν20 = 31.1 r36 = -38.86 d 36 = 33.68 r37 = 170.41 d 37 = 12.03 n21 = 1.48915 ν21 = 70.2 r38 = -42.17 d 38 = 2.20 n22 = 1.76168 ν22 = 27.5 r39 = -54.88 d 39 = 0.20 r40 = 322.72 d 40 = 1.90 n23 = 1.76168 ν23 = 27.5 r41 = 40.32 d 41 = 11.53 n24 = 1.51356 ν24 = 51.0 r42 = -298.39 d 42 = 1.10 r43 = 59.05 d 43 = 5.64 n25 = 1.48915 ν25 = 70.2 r44 = 3002.98 d 44 = 8.30 r45 = ∞ d 45 = 69.20 n26 = 1.51825 ν26 = 64.2 r46 = ∞

[0086]

[Table 2] Aspherical shape Reference spherical surface R = 254.65 Aspherical surface amount h ΔX Aspherical surface coefficient 70% (22.61) 0.04 μm A = B = 0 90% (29.07) 0.65 μm C = 2.534 × 10 ^-15 10% (32.30) 1.94 μm D = -3.133 × 10 ^-16 E = 1.845 × 10 ^-18 Parameter Zv = 4.99 Zv / Z = 0.3 FN1 = 1.55 FN3 = 0.99 h3m / h3T = 1.19 Δn = 0.17011 Numerical Example 3 f = 10.0 to 440 fno = 1: 1.75 to 3.0 2 ω = 57.6 ° to 0.72 ° r 1 = 397.20 d 1 = 5.50 n 1 = 1.72311 ν 1 = 29.5 r 2 = 182.95 d 2 = 0.70 r 3 = 181.76 d 3 = 23.08 n 2 = 1.43496 ν 2 = 95.1 r 4 = -601.22 d 4 = 0.30 r 5 = 178.22 d 5 = 18.30 n 3 = 1.43496 ν 3 = 95.1 r 6 = -4012.90 d 6 = 0.30 r 7 = 134.24 d 7 = 11.61 n 4 = 1.49845 ν 4 = 81.6 r 8 = 264.84 d 8 = variable r 9 = 1978.17 d 9 = 2.00 n 5 = 1.82017 ν 5 = 46.6 r10 = 61.00 d 10 = 4.30 r11 = -244.81 d 11 = 1.80 n 6 = 1 .77621 ν 6 = 49.6 r12 = 49.97 d 12 = 7.53 r13 = -56.56 d 13 = 1.80 n 7 = 1.82017 ν 7 = 46.6 r14 = 48.78 d 14 = 7.71 n 8 = 1.93306 ν 8 = 21.3 r15 = -227.11 d 15 = Variable r16 = 1717.21 d 16 = 6.39 n 9 = 1.49845 ν 9 = 81.6 r17 = -106.26 d 17 = 0.30 r18 = 200.29 d 18 = 2.50 n10 = 1.65223 ν10 = 33.8 r19 = 72.78 d 19 = 12.98 n11 = 1.59143 ν11 = 61.2 r20 = -125.34 d 20 = 0.20 r21 = 107.54 d 21 = 13.87 n12 = 1.62032 ν12 = 63.4 r22 = -71.24 d 22 = 2.50 n13 = 1.85501 ν13 = 23.9 r23 = -196.04 d 23 = 0.20 r24 = 124.29 d 24 = 3.50 n14 = 1.48915 ν14 = 70.2 (aspherical surface) r25 = 221.46 d 25 = variable r26 = (aperture) d 26 = 3.29 r27 = -53.23 d 27 = 1.80 n15 = 1.79013 ν15 = 44.2 r28 = 36.14 d 28 = 4.09 n16 = 1.81265 ν16 = 25.4 r29 = 167.11 d 29 = 5.57 r30 = -34.30 d 30 = 1.60 n17 = 1.73234 ν17 = 54.7 r31 = 34.37 d 31 = 10.20 n18 = 1.59911 ν18 = 39.2 r32 = -28.89 d 32 = 24.00 r33 = -471.13 d 33 = 5.79 n19 = 1.48915 ν19 = 70.2 r34 = -32.79 d 34 = 0.20 r35 = -53.92 d 35 = 2.20 n20 = 1.79013 ν20 = 44.2 r36 = 36.97 d 36 = 7.40 n21 = 1.50349 ν21 = 56.4 r37 = -66.22 d 37 = 1.10 r38 = 181.90 d 38 = 6.62 n22 = 1.55099 ν22 = 45.8 r39 = -30.85 d 39 = 2.20 n23 = 1.81265 ν23 = 25.4 r40 = -85.03 d 40 = 0.20 r41 = 73.62 d 41 = 5.14 n24 = 1.51977 ν24 = 52.4 r42 = -67.93 d 42 = 5.00 r43 = ∞ d 43 = 50.00 n25 = 1.51825 ν25 = 64.2 r44 = ∞

[0087]

[Table 3] Aspherical shape Reference spherical surface R = 124.297 Aspherical surface amount h Δn Aspherical surface coefficient 70% (20.03) 1.55 μm A = B = C = E = 0 90% (25.75) 11.6 μm D = 5 .997 × 10 ⁻¹⁴ 100% (28.61) 29.6 μm Parameter Zv = 9.19 Zv / Z = 0.209 FN1 = 1.28 FN3 = 0.83 h3m / h3T = 1.5 Δn = 0. 228 Numerical Example 4 F = 12.2 to 223.46 FNO = 1: 1.6 to 7.2 2 ω = 66.5 ° to 4.2 ° R 1 = 2455.41 D 1 = 5.40 N 1 = 1.69979 ν 1 = 55.5 R 2 = 271.91 D 2 = 28.94 R 3 = -267.58 D 3 = 3.009 N 2 = 1.69979 ν 2 = 55.5 R 4 = -2503.19 D 4 = 1.98 R 5 = 9738.25 D 5 = 3.00 N 3 = 1.64254 ν 3 = 60.1 R 6 = 224.83 D 6 = 14.59 N 4 = 1.76168 ν 4 = 27.5 R 7 = 1879.70 D 7 = 1.84 R 8 = 1282.45 D 8 = 13.52 N 5 = 1.62286 ν 5 = 60.3 R 9 = -242.57 D 9 = 0.30 R10 = 1074.61 D10 = 4.50 N 6 = 1.81265 ν 6 = 25.4 R11 = 150.07 D 11 = 20.80 N 7 = 1.48915 ν 7 = 70.2 R12 = -401.90 D 12 = 0.30 R13 = 160.26 D 13 = 16.10 N 8 = 1.48915 ν 8 = 70.2 R14 = 45982.91 D 14 = 0.30 R15 = 148.13 D 15 = 12.92 N 9 = 1.62286 ν 9 = 60.3 R16 = 512.54 D 16 = variable R17 = (95.44) D 17 = 2.40 N10 = 1.77621 ν10 = 49.6 Aspheric surface R18 = 42.25 D 18 = 9.16 R19 = -1689.53 D 19 = 2.20 N11 = 1.77621 ν11 = 49.6 R20 = 84.69 D 20 = 11.71 R21 = -46.36 D 21 = 2.20 N12 = 1.77621 ν12 = 49.6 R22 = 779.13 D 22 = 5.58 N13 = 1.93306 ν13 = 21.3 R23 = -92.60 D 23 = Variable R24 = 1110.01 D 24 = 8.90 N14 = 1.48915 ν14 = 70.2 R25 = -82.86 D 25 = 0.30 R26 = 325.37 D 26 = 12.18 N15 = 1.64254 ν15 = 60.1 R27 = -71.86 D 27 = 2.40 N16 = 1.81265 ν16 = 25.4 R28 = -222.32 D 28 = 0.30 R29 = 84.97 D 29 = 9.95 N17 = 1.48915 ν17 = 70.2 R30 =- 1089.44 D 30 = Variable R31 = (Aperture) D 31 = 5.46 R32 = -50.20 D 32 = 1.40 N18 = 1.65425 ν18 = 58.5 R33 = 40.78 D 33 = 4.55 N19 = 1.70443 ν19 = 30.1 R34 = 70.60 D 34 = 9.57 R35 = -39.52 D 35 = 1.50 N20 = 1.64254 ν20 = 60.1 R36 = -1029.62 D 36 = 9.38 N21 = 1.69417 ν21 = 31.1 R37 = -37.67 D 37 = 34.00 R38 = 69.80 D 38 = 12.39 N22 = 1.48915 22 = 70.2 1 R39 = -90.33 D 39 = 0.20 R40 = -496.87 D 40 = 2.00 N23 = 1.81265 ν23 = 25.4 R41 = 56.71 D 41 = 2.73 R42 = 111.78 D 42 = 7.91 N24 = 1.48915 ν24 = 70.2 R43 = -75.35 D 43 = 1.10 R44 = 54.78 D 44 = 8.11 N25 = 1.48915 ν25 = 70.2 R45 = 2543.16 D 45 = 8.30 R46 = ∞ D 46 = 69.20 N26 = 1.51825 ν26 = 64.1 R47 = ∞

[0088]

[Table 4] Aspherical surface: R17 parameter R = 95.446 h _W = 29.05 A = 0 h _M = 20.15 B = 0 h _T = 22.82 C = −6.22 × 10 ⁻¹¹ D = 1.5 × 10 ⁻¹³ E = −7.48 × 10 ⁻¹⁷

[0089]

As described above, according to the present invention, in the so-called four-group zoom lens, the change of the imaging magnification due to the magnification change of the variable power lens group and the image plane correction lens group, the refractive power of each lens group, and the like. By appropriately setting the F-number value and the like, and providing an aspherical surface on at least one lens surface where the incident height when an off-axis light beam or an on-axis light beam passes through the lens surface satisfies a predetermined conditional expression, The variation of spherical aberration due to magnification is reduced, and the variation of off-axis aberrations such as astigmatism, field curvature, and distortion aberration due to magnification is well-balanced to provide high optical performance over the entire magnification range. It is possible to achieve a zoom lens having a high zoom ratio with a large aperture ratio of about 1.6 at the wide angle end and a zoom ratio of about 18 to 40.

[Brief description of drawings]

FIG. 1 is a lens cross-sectional view at a wide-angle end according to Numerical Example 1 of the present invention.

FIG. 2 is a lens cross-sectional view at a wide-angle end according to Numerical Example 2 of the present invention.

FIG. 3 is a lens cross-sectional view at a wide-angle end according to Numerical Example 3 of the present invention.

FIG. 4 is an aberration diagram of a focal length of 12.2 according to Numerical Example 1 of the present invention.

FIG. 5 is an aberration diagram of a focal length of 25.38 according to Numerical Example 1 of the present invention.

FIG. 6 is an aberration diagram of a focal length of 46.58 according to Numerical Example 1 of the present invention.

FIG. 7: Focal length 162.21 of Numerical Example 1 of the present invention
Aberration diagram

FIG. 8 is a focal length 223.46 of Numerical Embodiment 1 of the present invention.
Aberration diagram

FIG. 9 is an aberration diagram of a focal length of 12.5 according to Numerical Example 2 of the present invention.

FIG. 10 is an aberration diagram of a focal length 22.0 according to Numerical Example 2 of the present invention.

FIG. 11 is an aberration diagram of a focal length of 45.3 according to Numerical Example 2 of the present invention.

FIG. 12: Focal length 170.0 of Numerical example 2 of the present invention
Aberration diagram

FIG. 13 is a focal length of 212.5 according to Numerical Example 2 of the present invention.
Aberration diagram

FIG. 14 is an aberration diagram of a focal length 10 according to Numerical Example 3 of the present invention.

FIG. 15 is a focal length of 19.49 according to Numerical Example 3 of the present invention.
Aberration diagram

FIG. 16 is a focal length of 69.78 according to Numerical Example 3 of the present invention.
Aberration diagram

FIG. 17 is a focal length of 256.6 according to Numerical Example 3 of the present invention.
Aberration diagram

FIG. 18 is a focal length 440.0 according to Numerical Example 3 of the present invention.
Aberration diagram

FIG. 19 is an explanatory diagram of variation in spherical aberration due to zooming of a conventional zoom lens.

FIG. 20 is an explanatory diagram of variation of spherical aberration due to zooming of the zoom lens according to the present invention.

FIG. 21 is an optical path diagram of a focal length 12.2 of a part of the optical system according to Numerical Example 1 of the present invention.

FIG. 22 is an optical path diagram of a focal length 162.21 of a part of the optical system according to Numerical Example 1 of the present invention.

FIG. 23 is an optical path diagram of a focal length 223.46 of a part of the optical system according to Numerical Example 1 of the present invention.

FIG. 24 is a lens cross-sectional view at a wide-angle end according to Numerical Example 4 of the present invention.

FIG. 25 is an aberration diagram of a focal length of 12.2 according to Numerical Example 4 of the present invention.

FIG. 26 is a focal length of 25.38 in Numerical Example 4 of the present invention.
Aberration diagram

FIG. 27 is a focal length of 46.58 in Numerical Example 4 of the present invention.
Aberration diagram

FIG. 28 is a focal length 162.2 according to Numerical Embodiment 4 of the present invention.
Aberration diagram of 1

FIG. 29 is a focal length 223.4 of Numerical Embodiment 4 of the present invention.
Aberration diagram of 6

FIG. 30 is an explanatory diagram of a change in off-axis aberration due to zooming of a conventional zoom lens.

FIG. 31 is an explanatory diagram of variation of off-axis aberrations due to zooming of the zoom lens according to the present invention.

[Explanation of symbols]

 F 1st group (focus group) F 1 front group focus group F 2 rear group focus group V 2nd group (variator) C 3rd group (compensator) R 4th group (relay group) G glass block SP diaphragm d d line g g-line ΔS sagittal image plane ΔM meridional image plane

Claims (3)

[Claims] 1. A first lens unit having a fixed positive refracting power, a second lens unit having a negative refracting power for zooming, and a positive lens unit for correcting an image plane variation due to zooming, in order from the object side. It has a third lens group having a refractive power and a fourth lens group having a fixed positive refractive power, and the focal lengths of the entire system at the wide-angle end and the telephoto end are fW and fT, the zoom ratio is Z, and the wide-angle end and the telephoto end are The F number is FNW, FNT, the first
The focal length and the F number of the group are f1, FN1, and the second
The group changes its image magnification in a region including the same magnification upon zooming,
The change of the lateral magnification is Z2, the imaging magnification of the third lens group changes in a region including the same magnification at the time of zooming, and the maximum incident height of the axial ray on the third lens group at the time of zooming. And the maximum incident heights at the telephoto end are h3m and h3T, respectively, the third group has at least one cemented lens surface, the refractive index difference between the medium before and after the cemented lens surface is Δn3, and the focal length of the third group. And F number are f
3 and FN3, 1.25 <FN1 <1.6, where FN1 = f1 /
(FT / FNT) 5 <Z2 0.2 <Z2 / Z <0.3 0.8 <FN3 <1.2, where FN3 = f3 /
At least one lens surface satisfying the condition of (2 × h3m) 0.17 <Δn3 and satisfying the condition of 1.15 <h3m / h3T in the third group has an aspherical surface. Zoom lens to do. 2. The aspherical surface has a shape in which the positive refracting power becomes stronger toward the peripheral portion of the lens, and the aspherical surface amount at 100%, 90%, and 70% of the lens effective diameter of the aspherical surface is ΔX ₁₀ , respectively. Assuming ΔX ₉ and ΔX ₇ 0 <ΔX ₇ / f3 <4 × 10 ⁻⁵ 9 × 10 ⁻⁶ <ΔX ₉ / f3 <3 × 10 ⁻⁴ 3 × 10 ⁻⁵ <ΔX ₁₀ / f3 <6 × 10 The zoom lens according to claim 1, wherein the condition ^-4 is satisfied. 3. A focus system, a zoom system, in order from the object side,
In the zoom lens composed of a relay system, the focal lengths at the wide-angle end and the telephoto end are fW and fT, the zoom ratio is Z, and
Incident height when the maximum angle of view ray at the wide-angle end is incident on the lens surface is hW, and when the maximum angle of view ray at the zoom position where the focal length fM is fM = fW × Z ^1/4 , is incident on the lens surface. Is hM, and the incident height when the maximum ray of the axial ray at the telephoto end is incident on the lens surface is hT. At least one lens surface satisfying the conditions 1.2 <hW / hM and hT <hW. A zoom lens with an aspherical surface.